Infrared (IR) detectors are sensors that convert incident IR radiation to an easy-to-process form of information (electrical voltage or current, deflection, etc). IR detectors have a wide span of applications including night vision and remote (contactless) temperature measurements. There are several types of IR detectors, mainly grouped under quantum infrared detectors and thermal infrared detectors.
Despite providing very high performance, quantum IR detectors of the prior art need cryogenic temperatures to operate which makes them costly and bulky devices.
On the other hand, thermal IR detectors of the prior art, usually called “bolometers”, does not need cryogenic temperatures to operate and can be manufactured using MEMS fabrication techniques.
Bolometers operate on the idea of measuring the temperature change of the surface which the incident IR radiation heats. There have been demonstrated various bolometer topologies with;                temperature dependent resistors, where the resistivity of a resistor changes with the temperature (IR→ΔT→ΔR→ΔV),        temperature dependent diodes, where the turn-on voltage of the diode changes with the temperature (IR→ΔT→ΔV),        thermal expansion based capacitive structures, where the increasing/decreasing temperature varies the gap of a capacitor structure (IR→ΔT→ΔC→ΔV).        
One problem with these bolometers is the saturation of the readout electronics due to self heating. Another drawback is the need of an ADC (analog-to-digital converter) to make the pixel data available for digital processing. ADC adds complexity and noise to the readout electronics with increased die area.
As an example of thermal IR detectors of the prior art, US 2004/0140428 A1 defines a pixel structure, forming one element of a focal plane array, including a bolometer having a detector and an insulator for measuring the incoming IR radiation by means of measuring the temperature change of the surface pixel structure.
In addition, US 2013/206988 A1 can also be an example of the thermal IR detectors of prior art. In US 2013/206988 A1, a detector having organic layers that can be utilized to produce a phototransistor for the detection of IR radiation is defined. The wavelength range of the defined IR detector can be modified by incorporating materials sensitive to photons of different wavelengths according to the invention. It has also been claimed that a photoconductor structure can be used instead of a phototransistor where the photoconductor can incorporate PbSe or PbS quantum dots and organic materials as part of an OLED structure. A detected IR image can be displayed to a user as the organic materials can be used to create an organic light-emitting device according to the invention.